<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0">

.div {
  width:100%; height:100px;
}
.child {
  float: left; 
}
.child {
  float:right;
}

html {
 font-size: 10px;
}
 
div {
 font-size: 1rem;
 height: 2rem;
 width: 3rem;
 border: .1rem solid #000;
}

var deviceWidth = document.documentElement.clientWidth > 1300 ? 1300 : document.documentElement.clientWidth;
document.documentElement.style.fontSize = (deviceWidth / 6.4) + 'px';

